In the case of displaying an image by projecting the image on a projection surface such as a screen using a projector, an adjustment corresponding to a relative positional relationship between the projector and the projection surface is generally performed. As such an adjustment, there can be cited a focus adjustment for adjusting the shift of the focus of the image (hereinafter also referred to as a “projection image”) projected on the projection surface, a keystone correction for correcting the distortion (hereinafter also referred to as a “keystone distortion”) of the image range of the projection image, and so on.
The focus adjustment and the keystone correction described above are performed by taking an image of a test pattern projected on the projection surface with a camera installed in the projector, and then obtaining the information necessary for the focus adjustment and the keystone correction based on the image (hereinafter also referred to as a “taken image”) thus taken (see PTL 1 and PTL 2).
In PTL 1, the operation is as simply explained below. Specifically, the light with even luminance is projected from the projector toward the screen, the reflected light from the screen is received, and the centroid position of the illuminance of the received light is detected. Then, the tilt angle of the screen is calculated based on the centroid position thus detected, and then the keystone distortion is corrected in accordance with the tilt angle thus calculated.
In PTL 2, the operation is as simply explained below. Specifically, focusing attention to four sides (upper, lower, right, and left sides) of the screen in the image taken by the imaging section, the ratios between the lengths of the two sides opposed to each other, namely the upper and lower sides and the right and left sides, are calculated. The ratio between the intensities of the lights respectively projected on the upper and lower areas is calculated based on the ratio between the upper and lower sides, and similarly, the ratio between the intensities of the lights respectively projected on the right and left areas is calculated based on the ratio between the right and left sides. Then, the test pattern based on the ratios of the light intensities is projected.